From Slashdot:
Agreed, but as someone who has just painstakingly managed to install Windows XP on a Dell XPS 1530 (which is officially Vista-only) I can attest to the fact that it's not "a bit of slowdown" - it's an imprecise measure but I'd say my laptop now "feels" at least two times faster/more responsive. We are talking about a pretty zippy dual core machine with 3 gigs of RAM and a powerful video card, too (256MB DDR3 nvidia 8600gt), which ran like treacle with Vista on it.
I have since played with another, similar Vista laptop trying to figure out what is doing all the damage. The worst individual offenders seem to be the (well documented) user account control bullshit which interferes with every aspect of the operation of the computer, and "supercache", which would have to be in the top 5 worst Microsoft innovations of all time.
For the uninitiated, supercache watches everything you do and records a log of what you cause to be loaded into memory and at what time/date it happens (this automatically introduces an overhead into every single memory related operation because Vista has to spend some resources on surveilling you). It then attempts to predict what you are going to use at a given point in time, and pre-caches as much of it as it considers to be reasonable. So for example, if I played Quake III every Wednesday night between 7-8pm, Vista would start grinding away at about 7pm on Wednesdays loading the texture files into RAM. Supercache apparently considers about 1.5 gigabytes on a system with 3 gigabytes of RAM to be a reasonable amount of physical memory to use for this process.
The net effect of all of the above is that Vista spends a hell of a lot of time sitting there churning away using your disks and RAM to load "stuff" into memory that you "might" need. All of this for the 1-2 seconds you are likely saving by not having to load Word or Quake III or whatever from disk should you happen to want to use it.
Turning UAC and Supercache off (both pretty straightforward once you know where to look) improves performance a lot - but not enough. Vista still has an offensively huge footprint and runs like a dog compared to XP.
Which returns me to the original point - XP is already a challenge to get running with some newer hardware. But if hardware manufacturers have the guts to stand up to Microsoft and keep producing XP versions of their hardware drivers (which should be trivial if they are doing 32 bit Vista drivers) then there's really very little we need from Microsoft.* XP is a stable, solid, mature OS which does what it does pretty well. I for one intend to keep using it into the foreseeable future.
* This is the main issue at the moment - most laptop manufacturers in particular have abandoned XP support on newer machines.
http://tech.slashdot.org/tech/08/03/25/0013235.shtml